1. Field of the Invention
The present invention relates to medical systems and, more specifically, to a system for generating speech and other sounds based on neural impulses.
2. Description of the Prior Art
Locked-in syndrome is a condition in which the subject has little or no motor control of the muscles needed to generate speech. In such a subject, communication may be effected by sensing eye movements. In one communication method, the movement of the subject's eye is correlated to a table of letters displayed on a computer screen and the subject spells out words by looking at the letters that forth the words that the subject wants to communicate. The result may be fed into a speech generator, which makes sounds corresponding to the words indicated by the subject. Alternately, inputs other than eye movement, such as motor-neural impulses, may be used to facilitate communications. In such systems, the input may control a cursor that moves over letters or icons on a computer screen and if the cursor rests on a letter for a sufficient amount of time, then the letter is added to a string of letters that eventually forms a word.
Such systems are limited in that they take a considerable amount of time to generate even simple words and they require the subject to expend extra mental effort in determining which letters are needed and the location of the letters on the table.
The region of the brain associated with speech generation is referred to as “Broca's area.” Generally, when one speaks, neuronal discharges form electrical spikes in the neurons in Broca's area. These discharges may be sensed from the local axons, where they are referred to as “action potentials.” Several different action potentials may be sensed in one location, with each different action potential possibly corresponding to a different mental action.
Currently, no system measures neuronal discharges or action potentials in the brain and transforms them directly into sounds such as phonemes, the most fundamental sounds that form words. Generating phonemes directly from action potentials in Broca's area would result in nearly real-time generation of speech. Giving a subject the ability to generate speech in a natural way would greatly facilitate communication between the subject and the outside world.
Therefore, there is a need for a speech generation system and method that employs a real-time natural mental process for the generation of sounds.